Most used high-vac pumps that are apparently 'seized-up' and sold cheaply, are easily repaired. Seizure is usually just a broken vane spring or the little shaft inside the spring is the culprit, also chunky sludge in oil compartment can cause binding. Easily replaceable vane springs & shafts , plus a good internal cleaning will get those old Cenco's & Welch's returned to duty once again.